This invention relates generally to electrochemically machining of metallic parts, and, more specifically, to electrochemically machining airfoils.
Electrochemical machining (hereinbelow also referred to alternatively as simply machining) is a conventional process in which a workpiece is typically provided with a positive voltage to create an anode, and an electrode is provided with a negative voltage to create a cathode. DC voltages between about 5-25 volts and up to about 15-30,000 amps are typically used. An electrolyte is then channeled in the space or gap between the workpiece and the electrode for electrochemically machining the workpiece. Such gap must be accurately maintained to avoid damaging sparking, or arcing, which would occur with gaps which are too small or cause too little electrolyte flow.
The prior art includes various methods for electrochemically machining airfoil blades, either singly or on a unitary integral bl(aded-d)isk assembly, i.e. blisk. Leading and trailing edges of an airfoil blade are especially difficult to machine precisely, and the prior art teaches various apparatus therefor.
Blisks having high camber, high twist and/or high solidity create substantial problems for economically electrochemically machining blades thereon. Camber refers to the angle of blade tip with respect to a centerline axis. Twist refers to the difference in camber angles between blade root and blade tip. And solidity refers to the number of blades with respect to the circumference of a blisk with high solidity indicating relatively closely-spaced blades.
An apparatus for efficiently and economically electrochemically machining blisks, therefore, must do so in relatively few operations and without utilizing relatively complex structures.